UNIDENTIFIED STORM-PETRELS, PUERTO MONTT, CHILE,
FEBRUARY, 2009
Jim Dowdall, Dublin, Ireland
Seamus Enright, Kerry, Ireland
Kieran Fahy, Wexford, Ireland
Jeff Gilligan, Oregon, USA
Gerard Lillie, Oregon, USA
Michael O’Keeffe, Kerry, Ireland
INTRODUCTION
In early February 2009 our party of four
Irish and two United States birders embarked on an exciting twelve day
sea-birding voyage from Valparaiso, Chile south around Cape Horn and then north
to Buenos Aires, Argentina, taking in various land stops along the route.
Using the local field guide as reference
(Jaramillo et al, 2003) we had noted Valparaiso’s
position near the southern edge of the expected range for many Humboldt Current
seabirds. So, in order to maximize our
seabird list a number of us decided to take in a pelagic off Valparaiso a couple of days prior to joining
our ship. On the pelagic we encountered a number of storm-petrels which at the time we found very
puzzling. They differed subtly from Wilson’s Storm-Petrels Oceanites oceanicus familiar to us all from the Northern Hemisphere. The features appeared intermediate between Wilson’s and Elliot’s
(White-vented) Storm-petrel Oceanites
gracilis, including quite a delicate “jizz”, a relatively narrow wing base and
a noticeably pale under-wing panel. Many
also displayed a lightly mottled vent/lower belly suggestive of Elliot’s. We
considered Elliot’s a remote possibility off Valparaiso so we were keen to put a name to
these birds. After some research we
concluded that these must be “Fuegian” Wilson’s Storm-petrel O. o. chilensis. Such was the interest sparked by these birds that
we began to closely inspect all storm-petrels thereafter. This soon paid off!
On February 4th, following a
very rewarding day’s land-based birding at Alerce
Andino National
Park we re-boarded our ship and began journeying south from
the city of Puerto Montt
through Seno de Reloncaví. Very soon we
were encountering our first storm-petrels
of the day. Seamus Enright was the first
to comment on the extent of white shown by these birds. It was soon apparent that all the birds which
we could see well showed lots of white on the vent/belly and on both the
upper-wing carpal area and under-wing greater coverts. This pattern was inconsistent with any known
taxon - once again we found ourselves
puzzled by storm-petrels in Chilean waters.
With the light beginning to fade some of us hastily tried to capture
images of these birds as we all tried to record what details we could from our
perch high up on the bow of the ship.
DESCRIPTION
By
sunset we had counted approximately 50 storm-petrels in Seno de Reloncaví. All of those photographed and observed well
appeared to be of the same form.
Unfortunately the viewing conditions precluded a detailed examination.
What follows is a description based on field observations backed up by
photographic evidence.
Most
striking was the extent of white in the plumage, suggestive initially of one of
the Fregetta storm-petrels. However a number of features appeared to rule
out that option, including the extent of dark on the flanks and the prominent
carpal bar. The birds appeared in fact to
be Oceanites Storm-petrels, similar
or perhaps slightly stockier than the chilensis Wilson’s Storm-petrels
which we had been encountering further north.
The whitish upper-wing and under-wing panels appeared more striking than
on any chilensis we had been observing. The white on the rump appeared to wrap
completely around the vent/lower belly, though from photographic evidence it is
hard to rule out the presence of perhaps some dark feathering on the sides and
centre of the vent.
DISCUSSION
These observations raise a number of tantalizing questions.
Why have these birds apparently gone undocumented until now?
Since
highlighting our observation it transpires that visiting birders have
seen similar birds in these waters and from the ferry crossing to
Chiloé Island, not far from Puerto Montt (A. Jaramillo, R. Matus and P.
Harrison pers. comm.). While compiling this paper we were amazed
to discover that Peter Harrison (pers. comm..) first encountered these
birds in circumstances similar to our own, whilst working aboard the
tour vessel M.V. Lindbald Explorer out of Puerto Montt in
1983/84. Harrison has seen these birds many times in the
intervening years. On two occasions, Harrison remarks he “was
lucky enough to have one land on the deck during the night and was able
to give them careful scrutiny. The wing measurements were 133mm
and 135mm” respectively. Using the only reference to hand
(Murphy, 1936) and based on the measurements he had obtained, Harrison
reached the conclusion these birds were chilensis.
It seems chilensis has a chequered history. Robert Cushman Murphy in “Oceanic Birds of South America” (1936) describes how the taxa Oceanites oceanicus chilensis was inadvertently first published nomen nudum
by W. B. Alexander in “Birds of the Ocean” (1928). The taxon was
later described in detail by Murphy (1936) and referred to as “Fuegian
Petrel”, a new subspecies of Wilsons Storm-Petrel. Subsequent to
that, for reasons we have yet to establish, the taxon was “dropped” as
a race of Wilson’s. Until very recently only two races of Wilsons
Storm-Petrel oceanicus and exasperatus were recognised in the literature, including by Harrison (1983, and in subsequent editions).
Interestingly
in relation to Wilson’s Storm-Petrel, Harrison notes “Cape Horn birds
may have pale vents (Naveen, pers. comm.).” It would appear Ron
Naveen was most likely referring here once again to chilensis which shows some pale mottling on the lower belly. Onley and Scofield (2007) have recently re-established chilensis as a third race of Wilson’s.
How far do the Puerto Montt storm-petrels range?
Obviously
we can only speculate. One would however expect such relatively
distinctive birds not to have gone unnoticed at a “well-watched”
location like for example Valparaiso. We did not see such
well-marked birds anywhere else on our voyage. Harrison (pers.
comm.) has reportedly observed these birds near Puerto Montt, in the
channel north of Chiloé Island and also in the Gulf of Penas,
approximately 500km south of Puerto Montt. The evidence therefore
suggests these birds are relatively localized and sedentary in nature.
Acknowledgments
We
would like to express our sincere thanks to Alvaro Jaramillo for his
expert advice and encouragement during the preparation of this
note. We would also like to thank Peter Burke, Peter Harrison,
Steve Howell, Santiago Imberti, Ricardo Matus, Mark Pearman, Christian
Savigne, Fabrice Schmitt and Rodrigo Reyes and Chris Wilson.
Reference
Flood. R.L. and Thomas B. 2007. Identification of ‘black-and-white’ storm-petrels of the North Atlantic. British Birds 100:7 407-442.
Jaramillo, A., Burke. P. and Beadle, D. 2003. Birds of Chile. Helm Publications, London
Naveen, R. (1981) Storm Petrels of the World. An Introductory Guide to their Identification. In: Birding 13(1981) S. 216-229.
Murphy, R.C. (1936). Oceanic
Birds of South America, a study of species of the related coasts and
seas, including the American quadrant of Antarctica based upon the
Brewster-Sanford collection in the American Museum of Natural History. The American Museum of Natural History. New York.
Onley, D. & Scofield, P. 2007. Albatrosses, Petrels and Shearwaters of the World. Helm Publications, London.
Harrison. P. 1983. Seabirds: An identification guide. Croom Helm, London.
Harrison. P. 1987. Seabirds of the World: a photographic guide. Helm Publications, London.
Pearman, M. 2000. First records of Elliot´s Storm Petrel Oceanites gracilipes in Argentina. El Hornero 15(2).
Robb. M., Mullarney. K and The Sound Approach. 2008. Petrels, Night and Day The Sound Approach
Saville,
S., Stevenson, B., & Southley, I. 2003. A possible sighting
of an ‘extinct’ bird – the New Zealand Storm-Petrel. Birding World 16: 173-175.
(Text and images are all
copyright of the authors).
Fig.
1
Unidentified storm-petrels, Seno de
Reloncaví, Puerto Montt, Chile, February 4th 2009. The
bird in the upper row of images may be a fresh juvenile while the lower two
rows appear to depict adults in moult. Note the extensive white on the vent and lower
belly joining the rump. There may be a slight
suggestion of dark feathering on the vent.
The upper-wing and under-wing bars were both very prominent though these
may appear slightly “exaggerated” here due to camera exposure. We advise a degree of caution when analysing
these slightly blurred, slightly over-exposed images.
All photos Michael O’Keeffe
Fig. 2
Artist’s
impression of the mystery Puerto Montt storm-petrel (bottom) together with chilensis and oceanicus/exasperatus Wilson’s
Storm-petrels and both a typical and an atypical, well-marked example of
Elliot’s Storm-petrel. The Puerto Montt
birds show less white on the belly and more white on the vent than typical Elliot’s
Storm-petrels. Elliot’s also shows a
clear divide between belly and rump, along the femoral tract, although this may
sometimes be faint or hidden. chilensis is a daintier bird than either
oceanicus or exasperatus and shows some plumage features suggestive of Elliot’s
including pale mottling on the belly and a paler underwing panel. Some indeed suspect chilensis may be closer to Elliot’s than Wilson’s.
Digital
sketch by Michael O’Keeffe.
Fig. 3
Map
of Southern South America showing the route of
our voyage. Within 24 hours of leaving Valparaiso we had left
the expected range of many Humboldt Current species including Elliot’s
Storm-Petrel. On the 3rd day
of the trip we encountered unidentified storm-petrels in Seno de Reloncaví, soon after
departing Puerto Montt (see inset).